This study evaluated the bond strengths between experimental Ti-20Cr-1X (X=Nb, Mo, Fe, Zr) alloys and porcelain (Duceratin). The results of this bond strength testing indicated that all the Ti-20Cr-1X alloys exceeded the lower limit value in the ISO 9693 standard for the 3-point bending test (25 MPa), and were all higher than that of commercially pure titanium (c.p. Ti). The coefficient of thermal expansion (CTE) values of all Ti-20Cr-1X alloys were higher than that of c.p. Ti, and this result of a closer match between CTEs shows the fact that the Ti-20Cr-1Mo alloy had a significantly higher bond strength than both the other Ti-20Cr-1X alloys and c.p. Ti.

Effect of heat treatment of Ag-Cu-Pd dispersant particles on the structure, mechanical properties and mercury vapor release rate of an Ag-Cu-Sn/Ag-Cu-Pd-based dental amalgam has been investigated. Experimental results indicate that crystallinity of dispersant Ag-Cu-Pd alloy increases with increasing HTT, with most notable increase occurring between 100 and 200 degrees C. Increasing HTT of Ag-Cu-Pd alloy does not change much of the mercury/alloy ratio for amalgamation, but largely reduces working/setting time of the amalgam. The Ag-Cu-Pd particles in 7 d-aged amalgam are comprised primarily of an outer Sn/Cu/Pd-rich zone and an inner Ag/Cu/Pd-rich zone with eutectic-type morphology and chemical distribution. The annealing-enhanced Pd segregation effect is most significantly observed in the amalgam derived from 300 degrees C-annealed Ag-Cu-Pd dispersant. This amalgam also has the highest compressive strength, highest DTS, and lowest creep rate. Higher annealing temperature causes mechanical property of the amalgam to deteriorate. The initial mercury vapor release rates of amalgams derived from 100, 200 and 300 degrees C-annealed Ag-Cu-Pd dispersant are significantly lower than that derived from 400 degrees C-annealed dispersant.

A series of Ag-Hg and Ag-Pd-Hg phases have been prepared by immersion in mercury and subsequent heat treatment of pure Ag and a series of Ag-Pd alloys. Phase transitions, along with the changes involved in morphology and chemistry, are investigated. Experimental results indicate that when mercury-immersed Ag discs are heat-treated at 90 degrees C for 12 h, large (>50 microm) crystals with Ag/Hg atomic ratios close to those of stoichiometric AgHg(2) form on the Ag surface. Heat treatment for 36 h causes these crystals to disintegrate into smaller (majority <10 microm) Ag(2)Hg(3) (gamma(1)) crystals. After 60 h, the stoichiometric gamma(1) crystals further breakdown into even smaller stoichiometric AgHg(beta(1)) crystals. The oft-referenced beta(1) phase Ag(1.1)Hg(0.9) is not supported in the present study. Addition of Pd to Ag has a dramatic effect on the morphology of the gamma(1) phase. With more addition of Pd, large-faceted and elongated gamma(1) crystals tend to grow in the midst of smaller matrix gamma(1) crystals. All three different Pd-containing crystals have (Ag + Pd)/Hg ratios very close to those of the stoichiometric gamma(1) phase, indicating that added Pd tends to replace Ag, rather than Hg, in the gamma(1) phase.

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